It is well known that various microorganisms are capable of producing metabolites associated with interesting biological activities. Such compounds are of potential interest for use in, e.g. the agricultural field where they are considered to constitute environmentally desirable alternatives to synthetically prepared compounds normally used, e.g. as biocides for controlling diseases and pests in valuable crops.
Although the search for such microbial metabolites has been a growing area of research during the last decade, only a minor number of useful biologically active metabolites has been identified and most biocides employed today are still synthetical compounds.
4-Ylidene tetronic acids with the general formula 2, is a rather newly discovered group of natural products. The distribution, synthesis, biosynthesis and biological activities of these compounds has been reviewed by Pattenden.sup.1. ##STR1##
These compounds are a sub-group of the tetronic acids with the general formula 1, which include biologically important natural products, such as vitamin C (i.e. a compound of formula 1 wherein R.sup.1 =OH and R.sup.2 =CHOHCH.sub.2 OH). ##STR2##
A variety of different biological activities have been reported for the tetronic acids, including antibiotic, anti-inflammatory, plant growth inhibitory, immunosuppressive and anti-coagulant effects.sup.1,2,3. However, the application of the compounds in therapy has often been precluded due to undesirable toxic side-effects.
The genus Fusiccocum is known as a producer of secondary metabolites; diterpenes.sup.4 and fatty acid derivatives.sup.5,6 have been reported from F. amygdali, but no compounds having structure and biological activity spectrum similar to the tetronic acids has been reported from said genus.